Updated 12:43 p.m. (CBS/AP) WASHINGTON D.C. - As many as 10 people have been shot after a shooting at the Washington Navy Yard on Monday morning, federal officials said.
At least six of those victims died from their wounds, federal and local officials told CBS News.
A gunman was neutralized, officials said, and security personnel are searching for a second gunman, although there has been no corroboration so far as to whether a second gunman exists.
The Navy has confirmed that a gunman has died, reports CBS News correspondent David Martin.
A law enforcement official told CBS News' Pat Milton the shooter apparently had a handgun, an AR-15 assault rifle, and a shotgun with him and was wearing dark blue clothing.
Speaking to reporters, Metropolitan police chief Cathy Lanier confirmed that one MPD officer was shot in "engagement" with the shooter inside the Navy Yard. One shooter believed to be involved has died, she confirmed.
Lanier said police are searching for two possible other shooters that may be dressed in military-style uniforms.
"The big concern for us right now is we have potentially two other shooters we have not located at this point," Lanier said at a press conference.
She described one possible shooter as a white male last seen around 8:35 or 8:40 this morning wearing a khaki or tan Navy-style uniform and a beret, armed with a handgun. Another possible shooter was described as a black male about 50 years old who may be carrying a long gun. Lanier said the man was possibly dressed in an olive-colored military-style uniform.
"We have no information to believe either of those folks are military personnel, but we do have information that hose persons are wearing military-style uniforms," Lanier said.
Eight civilians, one D.C. officer and one base security officer were among the victims, reports CBS affiliate WUSA. An officer was reportedly shot twice in the leg. The U.S. Park Police helicopter medevaced one person from the scene, reports the station.
An official told CBS News the number of victims could be higher because it is a "chaotic" scene.
Speaking to reporters, Dr. Janis Orlowski, the chief medical officer at MedStar Washington Hospital Center, said that three victims had been transported to her hospital, and all were alert and expected to survive.
One of the victims was a male Metropolitan police officer who suffered multiple gunshot wounds to his legs, Orlowski said.
Another victim, a woman, suffered gunshot wounds to her head and hands, and a third victim, also a woman, suffered a gunshot wound to her shoulder.
Orlowski said the hospital was told to expect more victims but it wasn't clear whether more would be transported.
Police and emergency crews gathered Monday morning outside the heavily-guarded Naval Sea Systems Command Headquarters building, where the shooting was reported.
Witnesses described a gunman opening fire from the fourth floor, aiming down on people in the first-floor cafeteria. Others said a gunman fired at them in a third-floor hallway.
Patricia Ward, who works at the Navy Yard, told reporters that she was in the cafeteria when she head three shots in quick succession and then four more shots.
"A lot of people were just panicking," Ward said. "No screams or anything, because we was just in shock."
The Navy says about 3,000 people work in the building. People inside the building have been directed to stay in place.
In a press release, the Navy said the shooting happened at approximately 8:30 a.m. ET.
Police are describing the shooter as a black male with a dark complexion, approximately five feet, ten inches to six feet tall, 170 pounds with a black shirt and black hat, reports the station.
United States Capitol Police said they are "providing mutual support & assistance to the Metropolitan Police Department" in a press release. They say the active shooter incident is "contained to the Navy Yard."
According to USCP, "Additionally, people may notice enhanced security operations being conducted by the USCP on the Capitol Grounds as a proactive, precautionary measure related to the active shooter incident at the Navy Yard."
Naval Sea Systems Command is the largest of the Navy's five system commands and accounts for a quarter of the Navy's entire budget.
It builds, buys and maintains the Navy's ships and submarines and their combat systems.
Police from multiple local and federal agencies were responding along with SWAT crews.
The FAA has issued a ground stop on all outgoing flights until further notice at Reagan National Airport for "security" reasons, and officials confirmed to WUSA that is related to the situation in the Navy Yard. Flights are operating as normal at Dulles Airport.